1. Field of the Invention
The present invention relates to a regulating cylinder unit installed in a silicon single-crystal pulling apparatus employing the Czochralski Method (CZ method), and relates to a jig for installing the regulating cylinders. The regulating cylinders can be used for the large charging and proper melting of polycrystalline silicon.
2. Description of Related Art
It is known that regulating cylinders (heat shielding cylinders) concentrically surrounding a single crystal being lifted can be used in silicon single-crystal pulling apparatuss to increase the lifting speed of single crystals and to avoid single-crystal dislocation induced by impurity contamination.
However, when polycrystalline silicon (the raw material of silicon single crystal) has to be fed into a quartz crucible in a situation wherein regulating cylinders have been installed in a silicon single-crystal pulling apparatus, the regulating cylinders become an obstacle to feeding operations. Therefore, the amount of raw material fed into the quartz crucible is smaller than the amount that can be fed into a quartz crucible that has not had regulating cylinders installed as above, and the productivity is thus low. Two methods of dealing with this drawback were proposed. These were: (a) dividing the regulating cylinders into two parts and raising one part of the regulating cylinders when feeding raw material (for example, Unexamined Japanese Patent Publication (kokai) No. Hei. 6-144986) as shown in FIG. 6, and (b) dividing the regulating cylinders into two parts, and raising one of the regulating cylinders so as to raise the other part of the regulating cylinders when feeding raw material (for example, Unexamined Japanese Patent Publication (kokai) No. Hei. 7-267777) as shown in FIG. 7.
However, in the above-mentioned (a) method, even if the amount of raw material fed into the quartz crucible is increased, the relevant part of the regulating cylinders near the crucible can not be raised. This has a detrimental effect on the melting environment of raw material. In the above-mentioned (b) method, the part of the regulating cylinders near the crucible can be raised, but in the process the regulating cylinders are raised in their entirety above the heater, so crucible cannot be raised, too. This increases the amount of electric power required by the melting operations and hindered the crystallization of single crystals due to quartz deterioration. In addition, there existed a danger that impurities may enter the melted liquid stored in the crucible due to the frictional movements occurring between the regulating cylinders.